1. Field of the Invention
The present invention relates to technology for decoding signals that have been encoded.
2. Description of the Related Art
When encoded signals are decoded, detection and correction of errors due to noise or the like are carried out. As one code for encoding signals, for example, low density parity check (expressed as LDPC below) code may be cited. When a signal encoded using the LDPC code is decoded (LDPC decoding), a decoded signal is multiplied by a check matrix (parity check matrix). In this way, detection of errors occurring with decoded signals is possible. Various methods have been proposed as methods of composing this check matrix (parity check matrix). For example, Patent Document 1 discloses a method of composing the check matrix (parity check matrix) in which a part of a matrix, defined according to a definition of a check matrix (parity check matrix) related to array codes, is modified to an upper triangular structure.
Patent Document 1: Japanese Patent Application, Laid Open No. 2003-115768
However, there are cases in which, according to the structure of the check matrix (parity check matrix), some errors occurring in the decoded signals cannot be detected.